I have POG OS with leather grip. It is looking nice but it is hard to play without overgrip (I am using Tourna or WilsonProWhite) - leather becomes slippery when wet.
You can try replace syntetic grip with leather+overgrip if synt. is too soft for your taste. I think Calleri is using leather grip without overgrip but he is using some white powder to prevent sliping

Leather definately has a nice feel. It sticks pretty well if you are not keeping it constantly wet, just a little moisture seems to make leather kind of tacky. It is fine with an overgrip, it does absorb sweat, and if you switch racquets mid set you will notice a weight difference.

Overgrip over leather grip feels much more secure and it seems to absorb moisture better with such combo. Leather is skin and naturally porous to absorb moisture better along with the overgrip. Synthetic is not as absorbent and once the overgrip is saturated with moisture, there is no where for the moisture to go but to stay on the grip. This can result on your grip slipping, and not feeling secure.